Method of producing a mixture of calcium nitrate and ammonium nitrate



Patented JulylZ, 1932- UNITED STATES PATENT I OFFICE nsaxus LABSSON, or BERLIN, GERMANY, ASSIGNOB r xonsrnfinenn-rarnnrm tained by reacting u wnarnxes-axrmnensmnscnxm,

or omens, swrrznnmnn IETHOD DI PRODUCING A. MIXTURE OI" CALCIUM NITRATE AND AMMIONIUMI NITRATE in Drawing. Application ma lay as, 1929, 8efla'l1Io.-866,079, and in sweaen June 5, ma.

This invention relates to an improved method of producing a mixture of calcium nitrate and ammonium nitrate.-

It has already been proposed to produce a mixture of calcium nitrate and ammonium nitrate from calcium carbonate which is obon calcium sulphate with ammonia and car on dioxide, by leaving ammonium sulphate solution in the calciumcarbonate and thereafter dissolving this mixture in nitric acid, the ammonium sulphate reacting with calcium nitrate formed to form calcium sulphate and ammonium nitrate. It

has prove that the calcium sulphate is then generalli obtained in such state that it can only wit diificulty be separated from the solution.

I have now' found that this inconvenience can be avoided by the calcium sulphate being first caused to cr stallize as semihydrate (2CaSO H O) and said semihydrate thereafter being recrystallized into gypsum (CaSO,.2H,O),

the gypsum then being obtained in such state that it can be easily separated from the solution. r

The semihydrate is, preferably, obtained the calcium carbonate being dissolved elther at a high temperature, say' C. or more, or at usual temperature and the reaction products being subsequently heated to a high temperature. In both cases the solution, however, has to be rather concentrated. The recrystallization of the semihydrate into gypsum is then brought about y the temperature of the solution being lowered or by its concentration being reduced or by these two ste s combined.

On e recrystallization gypsum in the form of short c stals'or fragments of crystals is, preferab added, the calcium s'ulphate being in this case chiefl precipitated on the crystals added. In manner a gypsum easy to settle is obtained, which can be separated from the solution of calcium nitrate and ammonium nitrate without difficulty.

In order to which are suitable as addition in the recrystallization of the calcium sulphate from semihydrate into gypsum and simultaneously to obtain the gypsum leaving the sys produce gypsum crystals tem in the shape 'of crystals of the size desired following manner. The solution produced together with the gypsum crystals of different sizes contained therein are transferred, after the finishing of the recrystallization, into an apparatuses for instance a classifier of a well-known type, in which the greater or stals are separated from the main portion 0 the solution, which still contains the smaller crystals in suspension. The solution freed from the great gypsum crystals together with the smaller gypsum crystals suspended therein is then transferred into a decantation tank, in which; the gypsum is permitted to settle so that the solution can e decanted, The bottom slime, consisting a small quantity of solutlon, is brou ht back to the recrystallization vessel in w ich the small crystals have opportunity to increase and thus to obtain the vdesired size. Generally small g psum crystals as well as great ones are 0 tained process so that the process may be carried on continuously.

fi'wample.405 grams of a filter cake obtamed by drawingoif the solution from 1,

the process is, preferably, carried out in-the .70 o the smaller gypsum crystals together with a in the recrystallization evolution of gases had ceased the solution was cooled to about C. and 40 grams of gypsum crystals suspended in a small quantity of concentrated calcium nitrate solution were added. After 4 to 5 hours the semihydrate primarily formed had recrystallized into gypsum in the shape of great and wellshaped crystals which could easily be separated from the solution.

What I claim is: a A

1. A method of producing a mixture of calcium nitrate and ammonium nitrate, which comprises reactingupon calcium sulphate with ammonia and carbon dioxide to form icalcium carbonate and ammonium sulphate, removing the greater part of the ammonium sulphate solution, dissolving the remaining slurry in nitric acid under such conditions of temperature and concentration that the calcium'sulphate by-product formed crystallizes as semihydrate, then causing the semihydrate to recrystallize into gypsum by lowering the temperature of the solution, and finally separating the gypsum from the solution produced.

2. A method of producing a mixture of calcium nitrate and ammonium nitrate, comprising reacting upon calcium sulphate with ammonia andcarbon dioxide to carbonate and ammonium sulphate, removing the greater part of the ammonium sulphate solution, dissolving the remaining slurry in nitric acid, subjecting the reaction products to a temperature of at least 80 (3., thus bringing the calcium sulphate by-product thereof to crystallize substantially as semihydrate in the solution, then causing the semihydrate to recrystallize into gypsum by lowering the temperature, and finally separating the gypsum from the solution.

3. A method of producing a mixture of calcium nitrate and ammonium nitrate, com:

- prising reacting upon calcium sulphate with monium sulphate solution, dissolving the re maining slurry in nitric acid, crystallizing the calcium sulphate by-product thereof as semihydrate by subjecting the reaction products to a temperature of at least 8Q O,

dissolving the remaining slurry in nitric acid, sub ecting the reaction with ammonia and carbon dioxide toadding thereto a solution containing small crystals of gypsum while cooling the mixture until the semihydrate recrystallizes into gypsum, separating the larger crystals of gypsum from the solution, and removing the principal portion of the solution therefrom, thereby rendering the remaining small gypsum crystals with their adherent solution suitable for return into the cycle of operation.

In testimony whereof I have signed my name.

MARKUS LARSSON.

form calcium v 

